2 * Copyright 1985, 1986, 1987, 1988 by the Massachusetts Institute
5 * For copying and distribution information, please see the file
8 * These routines perform encryption and decryption using the DES
9 * private key algorithm, or else a subset of it-- fewer inner loops.
10 * ( AUTH_DES_ITER defaults to 16, may be less)
12 * Under U.S. law, this software may not be exported outside the US
13 * without license from the U.S. Commerce department.
15 * The key schedule is passed as an arg, as well as the cleartext or
16 * ciphertext. The cleartext and ciphertext should be in host order.
18 * These routines form the library interface to the des facilities.
20 * spm 8/85 MIT project athena
23 #include <mit-cpyright.h>
26 #include <afs/param.h>
27 #include <afsconfig.h>
31 #include "des_internal.h"
33 #define XPRT_PCBC_ENCRYPT
36 extern int des_debug_print();
37 extern int des_ecb_encrypt();
40 * pcbc_encrypt is an "error propagation chaining" encrypt operation
41 * for DES, similar to CBC, but that, on encryption, "xor"s the
42 * plaintext of block N with the ciphertext resulting from block N,
43 * then "xor"s that result with the plaintext of block N+1 prior to
44 * encrypting block N+1. (decryption the appropriate inverse. This
45 * "pcbc" mode propagates a single bit error anywhere in either the
46 * cleartext or ciphertext chain all the way through to the end. In
47 * contrast, CBC mode limits a single bit error in the ciphertext to
48 * affect only the current (8byte) block and the subsequent block.
50 * performs pcbc error-propagation chaining operation by xor-ing block
51 * N+1 with both the plaintext (block N) and the ciphertext from block
52 * N. Either encrypts from cleartext to ciphertext, if encrypt != 0
53 * or decrypts from ciphertext to cleartext, if encrypt == 0
55 * NOTE-- the output is ALWAYS an multiple of 8 bytes long. If not
56 * enough space was provided, your program will get trashed.
58 * For encryption, the cleartext string is null padded, at the end, to
59 * an integral multiple of eight bytes.
61 * For decryption, the ciphertext will be used in integral multiples
62 * of 8 bytes, but only the first "length" bytes returned into the
65 * This is NOT a standard mode of operation.
70 des_pcbc_encrypt(in,out,length,key,iv,encrypt)
71 des_cblock *in; /* >= length bytes of inputtext */
72 des_cblock *out; /* >= length bytes of outputtext */
73 register afs_int32 length; /* in bytes */
74 int encrypt; /* 0 ==> decrypt, else encrypt */
75 des_key_schedule key; /* precomputed key schedule */
76 des_cblock *iv; /* 8 bytes of ivec */
78 register afs_uint32 *input = (afs_uint32 *) in;
79 register afs_uint32 *output = (afs_uint32 *) out;
80 register afs_uint32 *ivec = (afs_uint32 *) iv;
83 afs_uint32 t_input[2];
84 afs_uint32 t_output[2];
85 unsigned char *t_in_p = (unsigned char *) t_input;
86 afs_uint32 xor_0, xor_1;
90 if ((afs_int32) ivec & 3) {
91 bcopy((char *)ivec++,(char *)&xor_0,sizeof(xor_0));
92 bcopy((char *)ivec,(char *)&xor_1,sizeof(xor_1));
101 for (i = 0; length > 0; i++, length -= 8) {
104 if ((afs_int32) input & 3) {
105 bcopy((char *)input,(char *)&t_input[0],sizeof(t_input[0]));
106 bcopy((char *)(input+1),(char *)&t_input[1],sizeof(t_input[1]));
112 t_input[1] = *(input+1);
117 for (j = length; j <= 7; j++)
123 des_debug_print("clear",length,t_input[0],t_input[1]);
125 /* do the xor for cbc into the temp */
126 t_input[0] ^= xor_0 ;
127 t_input[1] ^= xor_1 ;
129 (void) des_ecb_encrypt(t_input,t_output,key,encrypt);
132 * We want to XOR with both the plaintext and ciphertext
133 * of the previous block, before we write the output, in
134 * case both input and output are the same space.
137 if ((afs_int32) input & 3) {
138 bcopy((char *)input++,(char *)&xor_0,sizeof(xor_0));
139 xor_0 ^= t_output[0];
140 bcopy((char *)input++,(char *)&xor_1,sizeof(xor_1));
141 xor_1 ^= t_output[1];
146 xor_0 = *input++ ^ t_output[0];
147 xor_1 = *input++ ^ t_output[1];
151 /* copy temp output and save it for cbc */
153 if ((afs_int32) output & 3) {
154 bcopy((char *)&t_output[0],(char *)output++,
155 sizeof(t_output[0]));
156 bcopy((char *)&t_output[1],(char *)output++,
157 sizeof(t_output[1]));
162 *output++ = t_output[0];
163 *output++ = t_output[1];
168 des_debug_print("xor'ed",i,t_input[0],t_input[1]);
169 des_debug_print("cipher",i,t_output[0],t_output[1]);
183 if ((afs_int32) ivec & 3) {
184 bcopy((char *)ivec++,(char *)&xor_0,sizeof(xor_0));
185 bcopy((char *)ivec,(char *)&xor_1,sizeof(xor_1));
194 for (i = 0; length > 0; i++, length -= 8) {
197 if ((afs_int32) input & 3) {
198 bcopy((char *)input++,(char *)&t_input[0],sizeof(t_input[0]));
199 bcopy((char *)input++,(char *)&t_input[1],sizeof(t_input[1]));
204 t_input[0] = *input++;
205 t_input[1] = *input++;
208 /* no padding for decrypt */
211 des_debug_print("cipher",i,t_input[0],t_input[1]);
218 (void) des_ecb_encrypt(t_input,t_output,key,encrypt);
221 des_debug_print("out pre xor",i,t_output[0],t_output[1]);
223 /* do the xor for cbc into the output */
224 t_output[0] ^= xor_0 ;
225 t_output[1] ^= xor_1 ;
226 /* copy temp output */
228 if ((afs_int32) output & 3) {
229 bcopy((char *)&t_output[0],(char *)output++,
230 sizeof(t_output[0]));
231 bcopy((char *)&t_output[1],(char *)output++,
232 sizeof(t_output[1]));
237 *output++ = t_output[0];
238 *output++ = t_output[1];
241 /* save xor value for next round */
242 xor_0 = t_output[0] ^ t_input[0];
243 xor_1 = t_output[1] ^ t_input[1];
247 des_debug_print("clear",i,t_output[0],t_output[1]);